Wildwood Zoo’s bighorn ram has died

MARSHFIELD — The city of Marshfield Parks & Recreation Department has announced the death of Rocky, the bighorn sheep ram at Wildwood Zoo. This is the second sheep death in just over two weeks. Following the loss of the lamb, both remaining adult sheep, including Rocky, were treated with antibiotics. Rocky passed away on Aug. 17 following his second checkup and round of antibiotics.

Though official necropsy results are pending, it is suspected that Rocky succumbed to the same disease as the lamb: Pasteurella multocida resulting in pneumonia. This is one of the most common causes of pneumonia in sheep and is one of the largest threats to wild bighorn sheep populations.

There are many contributing factors, mostly environmental, that predispose sheep to contracting pneumonia. Any extreme or rapid changes in climatic conditions or stressful situations can play a factor. The recent hot and humid weather likely played a role in the lamb’s and later Rocky’s infection.

The first sign of the disease within a flock is typically the death of the lambs. The mortality rate for infected animals is 50 percent to 90 percent and is even higher in newborns. This particular strain of bacteria can be transmitted from domesticated animals — such as dogs, cats, and other sheep — and some wildlife species.

It is impossible to determine what exactly brought these bacteria into the Wildwood herd. Anything from infected feed, wild or other zoo animals or staff, equipment movement between exhibits, or even the remaining ewe herself could have been the source.

Standard pretransport testing was conducted prior to the lamb and ewe traveling from Montana. However, the tests for the bacteria suspected to be responsible for these deaths was not among those. Additionally, the bacteria Pasteurella multocida is so common that its presence would not necessarily have precluded transport even had it been found.

In the immediate future, staff will monitor the remaining ewe for signs of infection. In the next year, staff will evaluate the exhibit to determine whether bighorn sheep are an appropriate species for display at Wildwood Zoo. Environmental conditions such as weather, substrate type, existing natural flora and fauna, and more can all play a role in how a specific species fares in a zoo environment. Additionally, natural history of the animal species itself as well as individual “personalities” of each exhibit animal can also play significant factors in overall animal health within zoos. Unfortunately, even with the wealth of knowledge available to zoo professionals, it is still difficult to foresee every possible issue that can arise during the exhibition of wild animals.

Historically, Wildwood Zoo displayed sheep, the most recent species being Barbados sheep. This species was removed from the collection in 2004 when the zoo switched to a North American Animal Collection. In 2014 Wildwood Zoo acquired Rocky in hopes of providing a unique North American wildlife viewing opportunity for patrons while also educating guests about the plight of bighorn sheep in the wild. Through exhibition of wild animals, Wildwood Zoo hopes to inspire awareness for and action supporting animals in need like the bighorn sheep. Though staff understood that keeping wild sheep in captivity can be difficult, they hoped the positives would outweigh the risks.

Wild bighorn sheep populations face many of the same health challenges as those at Wildwood Zoo. They are prone to infection and have little natural immunity or ability to fight disease. When one individual in a population gets sick, disease quickly moves through the other animals in the herd. According to the Washington Department of Fish and Wildlife (WDFW), preventing pneumonia outbreaks is one of the main concerns for sustaining Washington’s sheep herds. The WDFW also concedes that there is currently no effective treatment or preventive vaccine for pneumonia.

Though pneumonia is the most common cause of disease related mortality in sheep, there are other ailments that threaten sheep populations both in the wild and captivity. According to the National Park Service, a 1981 pinkeye epidemic in Yellowstone reduced the northern herd by 60 percent.